Combination of a teat cup and a flexible milk tube, a coupling piece, and a method of monitoring the integrity of the flexible milk tube

ABSTRACT

A combination of a teat cup and a flexible milk tube is shown. The flexible milk tube has a main duct and a plurality of secondary ducts for discharging milk from the teat cup and for applying vacuum in the teat cup. The main duct is confined by a duct wall extending around the main duct. The secondary ducts are included in the duct wall of the main duct. By including the plurality of secondary ducts in the duct wall of the main duct the flexible milk tube as a whole has a smaller cross-section than that of the known milk tube. The plurality of secondary ducts no longer need separate duct walls forming separate tubes either connected or not with the flexible milk tube comprising the main duct. This results in space saving.

CROSS REFERENCE TO RELATED APPLICATIONS

This application claims priority from Dutch patent application 1032063filed on 27 Jun. 2006, the contents of which are hereby incorporated byreference in their entirety.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The invention relates to the field of milking dairy animals and moreparticularly to a combination of a teat cup and a flexible milk tubehaving multiple ducts. The invention also relates to a method ofmonitoring the integrity of such a milk tube and to a coupling piece forconnecting of the milk tube to a further component.

2. Description of the Related Art

Devices are known for automatically milking a dairy animal, such as acow, in which a teat cup is connected to a flexible milk tube. The milktube may serve for discharging milk obtained by milking, applying vacuumto an end of a teat of the cow, applying a pulsating vacuum to thecircumferential surface of the teat of the cow, and for supplying cleanair to the teat cup. For these functions, the relevant flexible milktube may be provided with a plurality of ducts. Such a device is knownfrom WO-96/17509, the content of which is incorporated herein byreference, which discloses a case with three ducts. These three ductsare separated from each other. This means that the ducts are capable offulfilling different functions. A main duct substantially appliescontinuous vacuum and discharges the milk, a first secondary ductapplies the pulsating vacuum, and a second secondary duct supplies theair. Each of the main and secondary ducts is confined by its own ductwall. In fact, there are thus formed three separate tubes that areinterconnected over a substantial part of their length.

The known flexible milk tubes have certain disadvantages, including thefact that they may occupy a relatively large amount of space. This maybe of particular relevance in cases where each teat cup is separatelyconnected to the milking device and vacuum source. In such cases, aplurality of milk tubes from each of the four udder quarters of ananimal may run together over a considerable distance e.g. along a partof the robot arm of an automatic milking robot. Another disadvantage ofa plurality of separate tubes is that they can easily tangle and snag.In cases where the tubes are physically connected together, theresulting tube bundle is generally non symmetrical and may always tendto bend in one direction. In certain circumstances, this may beundesirable.

BRIEF SUMMARY OF THE INVENTION

The present invention aims at providing a combination of a teat cup anda flexible milk tube, that offers an alternative to prior artarrangements or in which the above-mentioned drawback is at leastpartially obviated. The invention aims in particular at providing acombination of a teat cup and a flexible milk tube, in which theflexible milk tube occupies less space than the flexible milk tube asdisclosed in WO-96/17509.

According to one aspect, the invention relates to a combination of ateat cup and a flexible milk tube. The flexible milk tube comprises amain duct and a plurality of secondary ducts for discharging milk fromthe teat cup and for applying vacuum in the teat cup. The secondaryducts are separated from the main duct. The main and secondary ductsextend substantially in an axial direction of the flexible milk tube.The main duct is confined by a duct wall extending around the main duct.The secondary ducts are incorporated into the duct wall of the mainduct.

By including the plurality of secondary ducts in the duct wall of themain duct the flexible milk tube as a whole may have a smallercross-section than that of the known milk tube. In this situation, theplurality of secondary ducts no longer need separate duct walls, whichduct walls form separate tubes that are either connected or not with theflexible milk tube comprising the main duct. This results in spacesaving. It is also understood that as a consequence of thisconstruction, the secondary ducts may not generally be separated fromthe main duct without damaging the integrity of that main duct, sinceboth share a common wall.

As it is common practice to design a duct wall of a main duct of aflexible milk tube as a relatively thick wall, a flexible milk tubehaving the same cross-section as a commonly used flexible milk tubecomprising only a main duct will even often suffice. Even if a somewhatgreater thickness of the duct wall is chosen in order to createadditional space for including the secondary ducts, the tube accordingto the invention will occupy in general less space than in the case ofthe secondary ducts being provided with their own duct walls, such as inthe state of the art.

In particular, the secondary ducts are equally distributed around thecircumference of the duct wall. This results in a flexible milk tubehaving a substantially comparable flexibility in all differentdirections.

In one embodiment, the flexible milk tube is provided with at leastfive, in particular six, more in particular eight, secondary ducts.According to the extent to which the number of secondary ducts islarger, the needed flow-through area of the collective secondary ductsis distributed over a larger number of secondary ducts, and it will bepossible for the individual secondary ducts to be designed smaller. Anupper limit to the desired number of secondary ducts is determined bythe increase of the flow-through resistance at the decrease of thecross-section of the secondary ducts and by practical considerationswith respect to the manufacture of the flexible milk tube. Furthermore,there is a relation between the cross-section and the number ofsecondary ducts. There has to be enough wall material left between thesecondary ducts to prevent the flexible milk tube from cracking anddistorting.

In a favourable embodiment, the secondary ducts, seen from an imaginarycentre line of the main duct, are laterally offset relative to eachother in a radial direction and overlap each other at least partially incircumferential direction. This means that possible damage of the ductwall of the flexible tube will in general first bring one of thesecondary ducts into connection with the surroundings of the flexiblemilk tube. This reduces the risk of the main duct, which is in generalused for discharging the milk, being contaminated from its surroundings.

Preferably, the main duct and the secondary ducts are generallyelliptical in shape. In the present context, elliptical is understood toinclude the particular case of circular. In particular the secondaryducts may also be elongated in cross-section, preferably in thecircumferential direction of the tube. Most preferably, the duct wallouter surface also has an elliptical shape, in particular round.Preferably this surface is also smooth to reduce the possible attachmentof contamination.

The invention also relates to a coupling piece for bringing a flexiblemilk tube into a coupled position with a component of a milkinginstallation, such as a teat cup. The coupling piece is provided with acoupling surface with a main aperture and a plurality of secondaryapertures that are intended to be brought into a flow-through connectionwith a main duct, and a plurality of secondary ducts, respectively, ofthe flexible milk tube. The secondary apertures are distributed aroundthe entire circumference of the main aperture. There is thus obtained acompact, space saving coupling for a flexible milk tube with a pluralityof ducts.

In one embodiment, the coupling piece is further provided with secondarypipes and a clamping ring. The secondary pipes are adapted to beincluded, in the coupled position, in the secondary ducts, near aproximal end of the flexible milk tube, i.e. the end of the flexiblemilk tube that faces the relevant coupling piece in the coupledposition. The clamping ring extends, in the coupled position, around theprojecting pipes. The secondary pipes in the secondary ducts give theflexible milk tube a greater rigidity at the place of the coupling piecethan in the case of a flexible milk tube according to the state of theart. This means that the clamping ring is capable of exerting sufficientclamping force on the flexible milk tube to reduce the risk of theflexible milk tube coming loose from the coupling piece.

The invention further relates to a method of monitoring the integrity ofa flexible milk tube, which flexible milk tube comprises a main duct anda plurality of secondary ducts for discharging milk from the teat cupand for applying vacuum in the teat cup. The method comprises applying apressure on at least a first group of the plurality of secondary ducts,which pressure deviates from an ambient pressure, determining thepressure in the first group of the plurality of secondary ducts,determining a control pressure value defined as the difference betweenthe measured pressure and a reference pressure, comparing the controlpressure value with a predetermined desired pressure value, or adevelopment in time of the control pressure value with a predetermineddesired development in time of a pressure value, and supplying an alarmsignal if the control pressure value, or the development in time of thecontrol pressure value, deviates to a predetermined extent from thepredetermined desired pressure value, or the predetermined desireddevelopment in time of the pressure value.

The method according to the invention thus provides information aboutthe flexible milk tube becoming leaky before—generally speaking—the mainduct that discharges milk is damaged itself and will possibly be broughtinto connection with the surroundings. This is particularly important inthe context of automatic milking devices that may be subjected toprolonged and intensive use without the presence of an operator tomonitor the condition of the tube. Furthermore, since damage to the milktube could be internal, this would not always be observable by externalinspection.

In particular, the supply of the alarm signal leads to the conveyance ofmilk from the flexible milk tube being stopped. This prevents possiblycontaminated milk from being conveyed.

In a favourable embodiment, a pressure is also measured in a secondgroup of the plurality of secondary ducts, or in the main duct, whichpressure in the second group of the plurality of secondary ducts, or inthe main duct, is used as the reference pressure. By monitoring apressure difference between different ducts of the flexible milk tube,accurate and reliable monitoring may be obtained.

According to a favourable embodiment of the invention, there is providedan automatic milking installation comprising four such assemblies ofmilk tube and teat cup and a robot device for automatically connectingthe teat cups to the udder quarters of a dairy animal. The milk tubesmay be co-extensive with at least part of a robot arm of the robotdevice. The reduced cross section of each tube ensures that the overallbulk of tubes carried by the arm is reduced. Alternatively, eachassembly may be individually carried by the robot arm. Even in thiscase, the reduced cross section and the uniform flexibility may beadvantageous.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will be explained in further detail with reference to theaccompanying drawing showing different embodiments of the invention, inwhich:

FIG. 1 shows a first embodiment of a flexible milk tube;

FIG. 2 shows a second embodiment of a flexible milk tube;

FIG. 3 shows a third embodiment of a flexible milk tube;

FIG. 4 shows a fourth embodiment of a flexible milk tube;

FIG. 5 shows a fifth embodiment of a flexible milk tube;

FIG. 6 shows a teat cup with a coupling piece, and

FIG. 7 is a cross-sectional view of the teat cup of FIG. 6 in thesituation in which it is coupled with a flexible milk tube.

DESCRIPTION OF ILLUSTRATIVE EMBODIMENTS

FIG. 1 shows a flexible milk tube that is indicated as a whole by thereference numeral 10. The flexible milk tube 10 comprises a main duct 12and a plurality, eight in this case, of secondary ducts 14. A duct wall16 extends around the main duct 12. The eight secondary ducts 14 areincluded in the duct wall 16. The main duct 12 is intended for applyinga vacuum in a teat cup (see FIGS. 6 and 7) and for discharging milk froma teat of an udder of a non-shown dairy animal. A first group ofsecondary ducts 14, or all secondary ducts 14, are intended forapplying, in a manner known per se, a pulsating vacuum in a part of theteat cup. A second group of secondary ducts 14 may possibly be intendedfor supplying clean air to the teat cup.

The duct wall 16 of the flexible milk tube 10 has a thickness that isusual for preventing the flexible milk tube 10 from cracking and/orpreventing the flexible milk tube 10 from getting closed or defect bykicking by the dairy animal. By disposing, according to the invention,the secondary ducts in said duct wall 16, it is not necessary to providea separate tube for the pulsating vacuum and/or for supplying clean air.Surprisingly, disposing the secondary ducts 14 in the duct wall 16 doesnot have an adverse effect on the cracking resistance of the flexiblemilk tube 10. In other words the flexible milk tube 10 according to theinvention has a cracking resistance that is comparable with, or issurprisingly even better than that of a flexible milk tube with the samewall thickness but without secondary ducts being included in the ductwall.

Furthermore, the flexible milk tube 10 according to the invention ismore flexible than a flexible milk tube that is not provided withsecondary ducts in the duct wall. This facilitates handling of theflexible milk tube 10 in practice. Moreover, the flexible milk tube 10needs less material than in the case of separate tubes (eitherinterconnected or not) being used for discharging milk and applying apulsating vacuum.

The eight secondary ducts 14 are distributed over the entirecircumference of the duct wall 16. In this case, the angular distance ofthe secondary ducts 14 relative to each other is always substantially 45degrees. More in general, the flexible milk tube 10 may be dividedimaginarily into four quarter circles, at least one secondary duct 14being present in each quarter-circle-shaped cross-section. A regulardivision of four, five, six, seven, eight, or more secondary ducts 14around the circumference of the duct wall provides substantiallyhomogenous characteristics of the flexible milk tube 10, theflexibility, for example, being comparable in all directions. Preferenceis given to the shown number of eight secondary ducts 14. From a pointof view of robustness it is advantageous if the secondary ducts 14 arelocated closer to the inner side than to the outer side of the duct wall16. In other words, the secondary ducts 14 are located closer to themain duct 12 than to the surroundings outside the flexible milk tube 10.

The main duct 12 has a relatively large cross-section, and consequentlya relatively large cross-sectional area that is available asflow-through area, relative to each of the individual secondary ducts14. However, the secondary ducts 14 provide collectively a flow-througharea that is sufficient for applying a pulsating vacuum. However, theflow-through area needed for this purpose is in general smaller thanthat of the flow-through area for discharging milk.

The flexible milk tube 10 has a smooth exterior wall. Although, withinthe scope of the invention, it is conceivable per se that the exteriorwall is provided with protrusions, or corrugations, a smooth exteriorwall is extra advantageous, because this reduces the risk of impuritiesand dirt sticking to the flexible milk tube 10.

FIG. 2 is a cross-sectional view of a variant of a flexible milk tube 20according to the invention. The flexible milk tube 20 comprises a mainduct 22, secondary ducts 25, and a duct wall 26. This embodiment differsfrom that of FIG. 1 in that the secondary ducts 25 have an elongatedshape, which elongated shape extends in the direction of the duct wall.This means that a smaller number of secondary ducts 25, in this casesix, will suffice, whereas there is achieved nevertheless a totalflow-through area that is comparable with that of FIG. 1. The elongatedshape is further advantageous upon detecting damage to the flexible milktube 20, as will be set out in further detail hereinafter.

FIG. 3 shows a flexible milk tube 30 with a main duct 32 and twelvesecondary ducts 35 that are included in a duct wall 36. An imaginarycentre line M, in this case also to be considered as the imaginarycentre line of the entire flexible milk tube 30, extends through themain duct 32.

The secondary ducts 35 are in a staggered position relative to eachother in radial direction relative to the centre lines, the end of eachof the secondary ducts 35 also overlapping an end of a next secondaryduct 35. In this manner, seen from the centre line M, in each radialdirection at least one secondary duct 35 is located in the duct wall 36.This means that possible damage from outside to the flexible milk tube30 will result in almost all cases in one of the ducts 35 being broughtinto connection with the surroundings before (also) the main duct isbrought into connection with the surroundings.

FIG. 4 shows a flexible milk tube 40 that is provided with a main duct42. The flexible milk tube 40 further comprises a first group ofsecondary ducts 44 and a second group of secondary ducts 45. Both thefirst group 44 and the second group 45 of secondary ducts are includedin a wall 46 extending around the main duct 42.

In the embodiment shown, the first group 44 of secondary ducts islocated at a smaller radial distance relative to an imaginary centreline M of the main duct 42 than the second group 45 of secondary ducts.However, the inverse situation is also possible. Furthermore, thesecondary ducts of both the first group 44 and the second group 45 maybe circular, or elliptical, or otherwise elongated in cross-section. Inuse, one of the two groups of secondary ducts may be used, for example,for applying a pulsating vacuum, whereas the other group may be used forapplying a pressure lower or higher than the atmospheric pressure, fordetecting damage to the flexible milk tube 44, as will be describedhereinafter in further detail.

FIG. 5 shows a flexible milk tube 50 with a main duct 52 and secondaryducts 54 that are included in a duct wall 56. In this case, the ductwall 56 is provided at its outer side with corrugations at the placewhere the secondary ducts 54 are located. This means that there isadditional material provided between the secondary ducts 54 and theouter side of the duct wall 56. The secondary ducts 54 are preferablylocated within an imaginary outer contour of the duct wall 56 extendingthrough the points on the outer side of the duct wall 56 having thesmallest radial distance relative to the imaginary centre line M. Theextent of corrugation of the flexible milk tube 50 is preferably limitedin order to reduce the risk of contamination of the flexible milk tube50. In other words, the variation in thickness of the duct wall 56 islimited, the greatest thickness being preferably no more than twice thesmallest thickness of the duct wall 56.

FIG. 6 is an indicative view of part of a teat cup 100 provided with acoupling piece 110. The coupling piece 110 comprises a cylindrical body112, one end of which is connected with the teat cup 100 and a secondend of which may be considered as a coupling surface 114. The couplingsurface 114 is provided with a main aperture 116 and a plurality, eightin this case, of secondary apertures 118. A main pipe 120 and secondarypipes 122 extend from the coupling surface 114. The main pipe 120 is ina flow-through connection with the main aperture 116. The secondarypipes are in a flow-through connection with the respective secondaryapertures 118.

A clamping projection 124 extends around the main pipe 120 in thevicinity of a distal end of it. A casing 130 extends around thecylindrical body. Said casing 130 extends, seen in axial direction, tobeyond the coupling surface 114. The casing 130 is provided withexternal screw thread that is capable of cooperating with internal screwthread of a clamping ring 132 (FIG. 7).

The secondary apertures 118 are all in a flow-through connection with afirst connecting area 136. In this embodiment, the first connecting area136 is a ring-shaped area constituted by a recess in the cylindricalbody 112.

FIG. 7 shows (part of) the teat cup 100 with coupling piece 110 in acoupled position with the flexible milk tube 10 of FIG. 1. By means of acorresponding adaptation of the secondary pipes, as shown in FIG. 6, theperson skilled in the art is capable of making the coupling piece ofFIG. 6 suitable for one of the other shown or non-shown flexible milktubes.

In use, a flexible milk tube 10 will be disposed on the coupling piece110 and the main duct 12 will be shifted on to the main pipe 120, overthe clamping projection 124, so that the main duct 12 will come into aflow-through connection with the main aperture 116. Moreover, thesecondary ducts 14 will be shifted on to the secondary pipes 122, forforming a flow-through connection of the secondary ducts to thesecondary apertures 118. An axial end of the flexible milk tube 10 isthen preferably disposed against the coupling surface 114.

After the flexible milk tube has been disposed, the clamping ring 132 isscrewed to the casing 130. Although such a measure is commonly used forsingle, thin-walled tubes, this has in general not appeared suitable forflexible milk tubes. Known flexible milk tubes often have on their outersides a non-round cross-section, which makes them less suitable forapplying a clamping ring. Besides, flexible milk tubes have in general agreat wall thickness. This results in that a possible clamping ring, inthe case of the known flexible milk tubes, leads mostly to the duct wallbeing pushed in, without resulting in a sufficiently clamping effect.Due to the inventive coupling piece, and the inventive flexible milktube, these drawbacks are obviated. Thanks to the invention, theflexible milk tube with a plurality of ducts may have, if desired, around outer circumference. Besides, the secondary pipes 122 ensure thatthe duct wall 16 becomes rigid. Due to this rigidity, the clamping ring132 has sufficient grip to achieve a substantial clamping. The clampingprojection 124 further increases the clamping effect of the clampingring 132 on the flexible milk tube 10.

In practice, each of the flexible milk tubes shown, as well as thecoupling piece shown, is capable of being used for discharging milk fromthe teat cup 100, applying a vacuum in the teat cup 100, applying apulsating vacuum in the teat cup 100, as well as for supplying clean airto the teat cup 100. For this purpose, the other (non-shown) end of theflexible milk tube 10 may also be provided with a coupling piece,comparable with coupling piece 110, for coupling to a not further shownmilking installation. Of course, coupling is also possible in anotherway, or by means of another type of coupling. A connecting area, or asecond connecting area, may also be located in the relevant couplingpiece. Also in the case of no coupling piece being provided at thesecond end of the flexible milk tube 10, a second connecting area willbe located elsewhere in the milking installation. The milkinginstallation may comprise a robot arm (not shown) for connecting theteat cups. Example of such milking installations are shown in U.S.application Ser. No. 11/643,715 filed 22 Dec. 2006 and U.S. Pat. No.7,044,079, the contents of both of which are hereby incorporatedentirely by reference.

The first connecting area 136 and the non-shown second connecting areaare each intended for interconnecting a group of the secondary ducts 14,in this case all secondary ducts 14, in a flow-through connection, atthe respective ends of the flexible milk tube 10. This means that thesecondary ducts collectively form an imaginary duct for fulfilling afunction, such as collectively applying a pulsating vacuum in the teatcup 100. The secondary ducts 14 may thus be considered as one virtualsecondary duct that is divided into a plurality of physical-secondaryducts. Of course, not all secondary ducts have to be interconnected bythe first and the second connecting area. There may even be provided athird, a fourth, or even more connecting areas, so that there areformed, as it were, groups of secondary ducts, it being possible foreach group to fulfil its own function. This means that, besides forapplying a pulsating vacuum, as described in the foregoing, it is alsopossible to use the secondary ducts for supplying clean air, or forother functions.

Besides, it will be possible to use one of the secondary ducts or, ifdesired, a non-shown additional secondary duct, as a conveying duct foran electric cable, for example for supplying electricity, or fortransferring a measuring signal. Of course, one secondary duct may alsobe provided with a plurality of electric cables, or a plurality ofsecondary ducts may be provided, if desired, with such electric cables.

In a favourable embodiment of one of the flexible milk tubes, or of anon-shown flexible milk tube with a main duct and a plurality ofsecondary ducts, the integrity of the relevant flexible milk tube ismonitored. Within the scope of the method there is applied a pressure tothe secondary ducts, or to a group of secondary ducts. This may be ahigher pressure, or a lower pressure, relative to the pressure in thesurroundings of the milk tube. If the relevant flexible milk tube is nowdamaged, in general first of all one of the secondary ducts will bebrought into connection with the surroundings. In order to increase thechance of this taking place, the secondary ducts with elongatedcross-sectional shapes, in particular the secondary ducts that overlapeach other, offer an additional advantage because they increase thechance that a secondary duct will be brought first, i.e. before the mainduct, into connection with the surroundings.

As soon as a secondary duct is brought into connection with thesurroundings, different things may occur. In the first place, in thecase of higher pressure, air, or another gas, will blow environmentaldirt from the secondary duct that has become leaky. The risk ofcontamination of milk in the main duct is thus reduced. Also in the caseof lower pressure in the duct that has become leaky, the risk ofcontamination is reduced owing to the fact that it is possible for dirt,if any, to be exhausted via the relevant secondary duct.

A second effect when a secondary duct becomes leaky is that the pressurein this secondary duct will deviate relative to a predeterminedpressure. It is possible to determine this pressure, for example bymeasurement. It is possible to deduce a control pressure value from themeasured pressure by determining the difference between the measuredpressure and a reference pressure. The reference pressure may simply bezero, or may have another constant value. However, the referencepressure may also be a measured pressure itself, for example a pressurein another group of the secondary ducts, or in the main duct. Thecontrol pressure value thus determined is compared with a predetermineddesired pressure value. If the control pressure value deviates to apredetermined extent from the predetermined desired pressure value, thisis an indication of leakage. Such a deviation may be observed andconverted into an alarm signal by a (non-shown) control unit. Such analarm signal may simply be a light signal and/or a sound signal.However, it is also possible to send, via a wire connection or awireless connection, a signal to a user located remote from the relevantmilk tube, for example at a farm or a central service centre. It is alsopossible to use the alarm signal in an advantageous manner as a signalfor removing the vacuum in the main duct and/or for ensuring in anothermanner that milk coming, via the main duct, from the damaged flexiblemilk tube of the relevant teat cup will no longer be supplied to a pointwhere it is collected with other (good) milk and discharged further.Instead, the milk discharge by the relevant flexible milk tube isstopped, or the milk in question is conveyed to a waste line.

In the above-described method it is also advantageous to make use of thevarying pressure in that part of the secondary ducts that is used forapplying a pulsating vacuum. In that case, the development in time ofthe relevant pulsating pressure is compared with a predetermineddevelopment in time for this pulsating pressure. If the relevantpulsating pressure levels, i.e. if it takes longer to increase and/ordecrease the pressure than in the case of an undamaged flexible milktube, this is an indication of leakage of the flexible milk tube. Apartfrom that, the above-described method steps may be followed.

Within the scope of the invention, various variants to the embodimentsshown and described are possible. For example, the main ducts andsecondary ducts do not have to be circular, but may also be ellipticallyshaped. In other words, main ducts and secondary ducts have across-sectional shape that corresponds to a continuous conic section.More in general, the main ducts and secondary ducts have cross-sectionalshapes with a flowing contour without acute angles. This facilitatescleaning of the main and secondary ducts and thus improves hygiene foruse as a milk tube.

In the embodiments shown, the flexible milk tubes have a substantiallyround outer circumference. This also contributes to the relevantflexible milk tubes having in several directions a substantially equalflexibility and this also improves for other reasons the ease ofhandling of the relevant flexible milk tubes. However, within the scopeof the invention, an elliptically shaped outer circumference is alsoimaginable. Said circumference still offers, for example, the advantageof reduced space occupation relative to flexible milk tubes according tothe state of the art. An elliptically or otherwise shaped outercircumference with a flowing contour has the advantage that dirt lesseasily sticks to the exterior wall of the relevant flexible milk tubethan in the case of the outer circumference being provided with acuteangles, corrugations, or other protrusions.

In the embodiments shown, the duct walls of the main ducts have aconstant thickness. Although such a constant thickness is advantageousfrom a point of view of material usage and space occupation, a varyingthickness is also possible within the scope of the invention. However,from a point of view of homogeneity of the characteristics and spaceoccupation, it is advantageous to limit such a variation to, forexample, a relation of 1:2 between the smallest and the largest wallthickness, respectively.

It is also possible to provide the pipes of the coupling piece shownentirely or partially loosely from the coupling piece. There may beprovided, for example, a set of secondary pipes that are looselyinserted into a flexible milk tube and thus function especially formaking the flexible milk tube rigid for the purpose of coupling. In avariant, at least a part of the loose secondary pipes areinterconnected, for example via an annular connecting element. It isadvantageous if one part of the secondary pipes is provided fixedly tothe coupling piece and a second part of the secondary pipes is providedloosely from the coupling piece. The fixed secondary pipes are thenintended, for example, for the secondary ducts supplying clean air,whereas the loose secondary pipes are intended for secondary ductsapplying pulsating vacuum. By connecting one part of the secondary pipesfixedly and another part non-fixedly with the coupling piece, there maybe formed a codification as a result of which there will only be one wayof coupling the coupling piece to the flexible milk tube.

The invention thus provides a combination of a teat cup and a flexiblemilk tube with a large number of advantages. The flexible milk tube hasa plurality of ducts that may be used for different functions in amilking installation. Despite the presence of a plurality of ducts, byincluding a plurality of secondary ducts in a duct wall, the flexiblemilk tube needs not to occupy more space than an already known flexiblemilk tube. Furthermore, for the inventive flexible milk tube lessmaterial is needed than for the commonly used flexible milk tubes with aplurality of ducts. The inventive flexible milk tube has a good crackingresistance and is at the same more flexible than known flexible milktubes.

Moreover, the flexible milk tube is very suitable for an inventivecoupling piece. The inventive coupling piece needs less space forcoupling to, for example, a teat cup than commonly used couplingsbetween flexible milk tubes and teat cups. Moreover, the inventivecoupling piece provides a more secure connection than the commonly usedcouplings.

In a method according to the invention, in which a flexible tubeaccording to the invention is preferably used, it is possible to detectthat the flexible tube becomes leaky, to prevent milk from beingcontaminated and to prevent possibly contaminated milk from beingsupplied to clean milk.

Thus, the invention has been described by reference to certainembodiments discussed above. It will be recognized that theseembodiments are susceptible to various modifications and alternativeforms well known to those of skill in the art without departing from thespirit and scope of the invention. Accordingly, although specificembodiments have been described, these are examples only and are notlimiting upon the scope of the invention.

1. A combination of a teat cup and a flexible milk tube, the flexiblemilk tube comprising a main duct and a plurality of secondary ductsseparated from the main duct, which main and secondary ducts extendsubstantially in an axial direction of the flexible milk tube fordischarging milk from the teat cup and for applying vacuum in the teatcup, and the main duct being confined by a duct wall extending aroundthe main duct and the plurality of secondary ducts being included withinthe duct wall of the main duct; further comprising a coupling piece forbringing the flexible milk tube into a coupled position with the teatcup, the coupling piece comprising a coupling surface with a mainaperture and a plurality of secondary apertures for flow-throughconnection with a main duct, and a plurality of secondary ducts of theflexible milk tube, respectively, the secondary apertures beingdistributed around the entire circumference of the main aperture;wherein the combination further comprises secondary pipes, the secondarypipes comprising the secondary apertures and being inserted in thecoupled position into the secondary ducts in the vicinity of a proximalend of the flexible milk tube.
 2. The combination as claimed in claim 1,the plurality of secondary ducts being distributed over an entirecircumference of the duct wall.
 3. The combination as claimed in claim1, the flexible milk tube being provided with at least five secondaryducts.
 4. The combination as claimed in claim 1, the secondary ductsbeing laterally offset relative to each other in a radial direction withrespect to the main duct and overlapping each other at least partiallyin a circumferential direction.
 5. The combination as claimed in claim1, which combination is further provided with a first connecting areaand a second connecting area, which are located in the vicinity of afirst end and a second end, respectively, of the flexible milk tube,each being in flow-through connection with at least one group of theplurality of secondary ducts, for forming a collective duct.
 6. Thecombination as claimed in claim 1, the main duct having across-sectional area that is larger than the collective cross-sectionalarea of two of the secondary ducts.
 7. The combination as claimed inclaim 6, the main duct having a cross-sectional area that is at leastequal to the collective cross-sectional area of all secondary ducts. 8.The combination as claimed in claim 1, an outer side of the duct wallhaving a substantially elliptical cross-sectional shape.
 9. Thecombination as claimed in claim 1, the secondary ducts havingsubstantially elliptical cross-sectional shapes.
 10. The combination asclaimed in claim 1, the secondary ducts having substantially elongatedcross-sectional shapes, which elongated shape extends substantially in acircumferential direction of the duct wall.
 11. A milking installationcomprising four assemblies of a teat cup and a flexible milk tube, eachassembly being as claimed in claim
 1. 12. The milking installation asclaimed in claim 11, further comprising a robot arm for automaticallyplacing the teat cups onto the teats of a dairy animal.
 13. The milkinginstallation as claimed in claim 12, wherein the flexible milk tubes arecarried by the robot arm.
 14. The milking installation as claimed inclaim 1, further comprising a clamping ring, the clamping ringextending, in the coupled position, around the secondary pipes.
 15. Themilking installation as claimed in claim 1, further comprising ameasuring device for measuring a pressure in at least a first group ofthe plurality of secondary ducts.
 16. The milking installation asclaimed in claim 1, further comprising a control unit for monitoring theintegrity of the flexible milk tube, the control unit for: receiving ameasurement of a pressure in at least a first group of the plurality ofsecondary ducts; determining a control pressure value defined as thedifference between the measured pressure and a reference pressure;comparing the control pressure value with a predetermined desiredpressure value, or a development in time of the control pressure valuewith a predetermined desired development in time of a pressure value;and supplying an alarm signal if the control pressure value, or thedevelopment in time of the control pressure value, deviates to apredetermined extent from the predetermined desired pressure value, orthe predetermined desired development in time of the pressure value. 17.The milking installation as claimed in claim 16, wherein the controlunit is further adapted for stopping discharge of milk through theflexible milk tube in response to the alarm signal.
 18. The milkinginstallation as claimed in claim 16, wherein the control unit is furtheradapted to receive a measurement of a pressure in a second group of theplurality of secondary ducts, or in the main duct, which pressure in thesecond group of the plurality of secondary ducts, or in the main duct,is used as the reference pressure.
 19. A combination of a teat cup and aflexible milk tube, the flexible milk tube comprising a main duct and aplurality of secondary ducts separated from the main duct, which mainand secondary ducts extend substantially in an axial direction of theflexible milk tube for discharging milk from the teat cup and forapplying vacuum in the teat cup, and the main duct being confined by aduct wall extending around the main duct and the plurality of secondaryducts being included within the duct wall of the main duct; furthercomprising a coupling piece for bringing the flexible milk tube into acoupled position with the teat cup, the coupling piece comprising acoupling surface with a main aperture and a plurality of secondaryapertures for flow-through connection with a main duct, and a pluralityof secondary ducts of the flexible milk tube, respectively, thesecondary apertures being distributed around the entire circumference ofthe main aperture; wherein the combination further comprises secondarypipes the secondary pipes comprising the secondary apertures and beinginserted in the coupled position into the secondary ducts in thevicinity of a proximal end of the flexible milk tube, and furthercomprising a clamping ring, the clamping ring extending, in the coupledposition, around the secondary pipes.